Chlorosulfonated polyethylene elastomers and chlorosulfonated ethylene copolymer elastomers have been found to be very good elastomeric materials for use in applications such as wire and cable jacketing, molded goods, automotive hose, power transmission belts, roofing membranes and tank liners. These materials are noted for their balance of oil resistance, thermal stability, ozone resistance and chemical resistance.
Historically, a wide variety of polyolefin polymers, including ethylene and propylene homopolymers and copolymers, have been utilized as the starting polymers (i.e. “base polymers” or “base resins”) for manufacture of chlorosulfonated products. The majority of base polymers employed in the manufacture of chlorosulfonated elastomers have been polyethylene types, e.g. low density polyethylene (LDPE), linear low density polyethylene (LLDPE) and high density polyethylene (HDPE). Most of the ethylene homopolymers and copolymers employed to make these elastomers are polymerized by a high pressure free radical catalyzed process or by a low pressure process using Ziegler-Natta or Phillips type catalysts.
Chlorosulfonated elastomers based on highly branched LDPE usually have desirable extrusion and flow properties, but low physical properties. Chlorosulfonated elastomers based on linear HDPE or LLDPE base polymers generally have superior physical properties, but inferior extrusion properties.
U.S. Pat. No. 5,668,220 discloses chlorinated and chlorosulfonated elastomers that contain 20-50 weight percent chlorine and 0.8-2.5 weight percent sulfur. These elastomers are made from ethylene/alpha-olefin copolymers that were polymerized in the presence of a single site or metallocene catalyst. Such ethylene copolymers have improved extrusion or flow properties when compared to polymers having the same molecular weight distribution, but produced using a Ziegler-Natta catalyst.
Japanese Kokai Hei 2[1990]-18681 discloses polyolefin ionomers containing —SO3M groups, where M is a univalent cation. The ionomers are made by reacting a portion of the —SO2Cl groups on a chlorosulfonated polyolefin with base. Chlorosulfonated polyethylene is described as having between 25-36% chlorine. However, ionomers made from chlorosulfonated ethylene/alpha-olefins of the type taught in U.S. Pat. No. 5,688,220 are not disclosed.
Ethylene based elastomers (e.g. EP and EPDM) are utilized as viscosity modifiers for oils in automotive and industrial applications. These polymers are readily soluble and stable in paraffinic and naphthenic oils whereas more polar polymers (e.g. ethylene acrylic or methacrylic copolymers and highly chlorinated ethylene polymers) are not. Some of these oil additive polymers are also functionalized with reactive groups in order to incorporate stabilizers for oil systems.
It would be desirable to have partially neutralized (i.e. ionomers) of chlorosulfonated ethylene/alpha-olefin copolymers having less than 20 weight percent chlorine and a low level of residual crystallinity for use in oil based solutions and emulsions. In some of these applications where solution viscosity must be balanced with oil solubility and polymer thermal stability, it would be desirable to employ copolymers manufactured with a single site catalyst.